This invention relates to polyacetal resin compositions and molded articles made therefrom having improved wear properties. In particular, the invention is concerned with molded articles made from a novel polyacetal resin composition useful in low wear applications such as for the replacement of metals or in improving plastic to metal wear performance.
Polyoxymethylene polymers having recurring --CH.sub.2 O-- units, have been known for many years. These polymers may be prepared by the polymerization of anhydrous formaldehyde or by the polymerization of trioxane, which is a cyclic trimer of formaldehyde. Also known is the preparation of oxymethylene copolymers by copolymerizing trioxane with cyclic ethers such as dioxolane. These copolymers are also used as molding resins, U.S. Pat. No. 3,027,352. Polyacetal terpolymers such as formed by polymerizing a blend comprising a major amount of trioxane, a small amount of a polyfunctional epoxy-containing compound having two copolymerizably reactive groups such as butanediol diglycidyl ether and a minor amount of ethylene oxide, U.S. Pat. No. 3,445,433 are also known and have use as molding compositions.
Present state of the art concerns have been to impart desired physical properties to polyacetal resins by inclusion of additives. For example, small amounts, e.g. less than 1 wt. %, of each polyethylene glycol and glyceryl monostearate have been shown to impart antistatic properties to polyacetal resins without excessive waxy bleeding on the surface of the molded article, excessive lubrication, discoloration, and reduction in thermal stability which often results upon addition of antistatic agents, U.S. Pat. No. 4,274,986. This reference is herein incorporated by reference. Polydimethylsiloxane addition has been shown to improve the wear properties of polyacetal resins, U.S. Pat. No. 4,472,556. Melt flow properties of oxymethylene polymers have been improved by addition of silicon oil, U.S. Pat. No. 3,491,048.
It is an object of the present invention to improve the wear properties of oxymethylene polymers, in particular, oxymethylene polymers with antistatic properties and render such polymers useful in the molding of component parts as replacements for metal components or for component plastics where plastic to metal and plastic to plastic wear properties are important.